1. Field of the Invention
This invention relates in general to a pressure-pulse-wave detecting probe including a sensor portion which has a press surface that is to be pressed against an artery of a living subject via a body surface of the subject such that a pressure pulse wave generated by the artery is detected by at least one pressure detecting element arranged on the press surface. More particularly, the invention is concerned with such a pressure-pulse-wave detecting probe of manually-operable type in which a pressing condition of the press surface of the sensor portion is adjustable manually by an operator.
2. Discussion of the Related Art
There is known a pressure-pulse-wave detecting probe including a sensor portion which has a press surface that is to be brought into pressing contact with a predetermined portion of a living subject and pressed against an artery of the subject via a body surface of the subject such that a pressure pulse wave generated by the artery is detected by at least one pressure detecting element arranged on the press surface.
For assuring accurate detection of the pulse wave with use of such a pressure-pulse-wave detecting probe, it is necessary to position the press surface of the sensor portion relative to the artery of the living subject such that the above-described at least one pressure detecting element is positioned right above the artery, and also to force the press surface against the artery with a suitable pressing force. To this end, there is proposed an apparatus for controlling the position of the press surface and the pressing force applied to the artery of the subject. Examples of such an apparatus are disclosed in JP-A-H11-19054 and JP-A-H11-9562 (which are publications of unexamined Japanese Patent Applications laid open 1999).
In each of the apparatuses disclosed in the Japanese publications in which a plurality of pressure detecting elements are provided on the press surface, when the pressure-pulse-wave detecting probe is mounted on a predetermined portion of a living subject, an optimum position of a pressure-pulse wave sensor (i.e.;, the sensor portion) is automatically determined based on a comparison among magnitudes of the pressure pulse waves which are detected by the respective pressure detecting elements. After the determination of the optimum position of the pressure-pulse-wave sensor, the pressing force acting on the pressure-pulse-wave sensor is gradually changed, and an optimum value of the pressing force is automatically determined based on the magnitudes of the pressure pulse waves detected by the pressure detecting elements in process of the gradual change of the pressing force.
In the apparatus disclosed in JP-A-H11-19054, after the optimum position and the optimum pressing force value have been thus determined, the pressing condition is continuously monitored during the detection of the pulse wave. More specifically described, a determination as to whether the optimum pressing force value is maintained is repeatedly made, on the basis of a pressure distribution curve representative of the magnitudes of the pressure pulse waves detected by the respective pressure detecting elements, so that the pressing force is automatically adjusted or changed as needed. In the apparatus disclosed in JP-A-H11-9562, after the determinations of the optimum position and pressing force value, a determination as to whether the optimum position is maintained is repeatedly made on the basis of an amplitude distribution curve representative of amplitudes of the pressure pulse waves detected by the respective pressure detecting elements, so that the position of the pressure-pulse-wave sensor is automatically adjusted or changed as needed.
Each of the above-described apparatuses, arranged to automatically determine the optimum position and pressing force and then maintain them as described above, is capable of accurately detecting the pressure pulse wave. In such an apparatus, however, since the pressure-pulse-wave detecting probe has to be equipped with a moving device for moving the pressure-pulse-wave sensor and also a pressing device for pressing the pressure-pulse-wave sensor, the pressure-pulse-wave detecting probe inevitably has a complicated structure. The probe having the complicated structure, when it is mounted onto a living, subject, requires a somewhat cumbersome operation, and limits a portion of the subject onto which the probe is mountable. Further, the complicated structure of the probe leads to an increase in the cost of manufacture of the apparatus.
Besides the pressure-pulse-wave detecting probe equipped with the moving device and the pressing device, there is known a pressure-pulse-wave detecting probe of manually-operable type, which is to be held, by a hand of operator (e.g. a person who measures the pressure pulse wave) or by a suitable fixture such as a clip and a band, in a predetermined portion of a patient's body during detection of the pulse wave. In operation with such a manually-operable-type probe, the press surface is positioned manually by an operator, relative to the artery of the living subject, and is then pressed manually by the operator, against the artery of the subject via the body surface of the subject. That is, the pressing condition of the press surface of the sensor portion is adjustable manually by the operator. Owing to the absence of the above-described moving and pressing devices, the manually-operable-type probe can be easily mounted onto a living subject, without limiting a portion onto which the probe is mountable.
However, the conventional manually-operable-type pressure-pulse-wave detecting probe has a difficulty in determining the optimum pressing position and pressing force and maintaining them.